Article date: 1992/1/1
PubMed ID: 1374543
Journal name: Neuroscience (ISSN: 0306-4522)
The effect of intracellular and extracellular pH on GABA-gated Cl- conductance was studied using H(+)-selective microelectrodes and a three-microelectrode voltage clamp in crayfish leg opener muscle fibres in bicarbonate-free solutions. Experimental variation of intracellular pH in the range 6.4-8.0 did not affect the GABA-gated conductance. In contrast to this, the GABA-gated conductance was sensitive to changes in external pH. Raising the external pH from 7.4 to 8.4 decreased the GABA-gated peak conductance observed immediately following application of GABA by 30%, and a change from 7.4 to 6.4 produced an increase of 26%. The effect of extracellular pH on the GABA-gated peak conductance was approximately linear in the pH range 6.4-8.9. A slight decrease in the slope of the pH-conductance relationship was evident in the pH range 5.4-6.4. The desensitization of the GABA-gated conductance was also affected by external pH. At pH 6.9 the conductance produced by 1 mM GABA showed a desensitization of about 15%, and at pH 8.9 this value was 34%. Raising the external pH in the presence of GABA decreased the GABA-gated peak conductance and increased the fractional desensitization, while lowering the external pH produced opposite effects, and was capable of repriming the conductance from a desensitized state to the non-desensitized state. The above results show that the GABA-gated conductance is sensitive to changes in external pH in the physiological range, and suggest that pH-dependent changes in the postsynaptic efficacy of GABA-mediated inhibition may contribute to H+ modulation of neuronal excitability.
Author List: Pasternack M, Bountra C, Voipio J, Kaila K
Publication Types: Journal Article; Research Support, Non-U.S. Gov't
Substances mentioned in the article: Chloride Channels; Ion Channels; Membrane Proteins; Muscimol; gamma-Aminobutyric Acid;
Mesh terms: Animals; Astacoidea; Chloride Channels; Dose-Response Relationship, Drug; Hydrogen-Ion Concentration; In Vitro Techniques; Ion Channels/physiology; Kinetics; Membrane Potentials/drug effects; Membrane Proteins/drug effects; Muscimol/pharmacology; Muscles/drug effects; gamma-Aminobutyric Acid/pharmacology;